1. Field of the Invention
The present invention relates to a method of fabricating an optical semiconductor device.
2. Related Background Art
In order to fabricating an optical semiconductor device, an alignment mark for lithography is formed on a wafer. It is known that a protecting film is formed on the alignment mark in order to prevent the alignment mark from being deformed or damaged during processes, as disclosed in Japanese Unexamined Patent Application Publication No. 2001-251007.